1978 Pontiac Trans Am

Feature Article from Hemmings Muscle Machines

You thought performance died after '70. The old muscle cars of your youth were left out to pasture, and you watched them rust into the landscape. You settled into the family lifestyle, piloting a full-size wood-grained wagon across six states to get to some cheesy tourist attraction. That's when the Trans Am hit the silver screen dressed in black, and the twinge of horsepower tickled your right foot again. You wanted one, but responsible reality returned.
Now it's 2008, the kids have graduated, the wagon is long gone and you've just spotted a 1977 Trans Am for sale nearby. Before you jump to the phone, stop and consider the 1978 models. Sure, they look the same, but the 1978 W72 version had a bigger surprise under the hood for those who waited an extra year--a full 20hp more. They also handled much better, thanks to the optional WS6 package. Better still, you could get it with a four-speed. While your mind begins to churn over the possibilities, here are a few more nuggets for you to consume.
ENGINES
An unmolested 1978 T/A should contain only one of two block types of varying cubic displacements: the famed Pontiac 400--introduced to gearheads in the 1967 models and later referred to as the 6.6L--or the Oldsmobile-built 403, based on the small-block Olds V-8. All 400s, no matter which year they were constructed, feature a bore and stroke measuring 4.12 x 3.75 inches, as well as five main bearings. Compression ratios varied from year to year, accomplished through the use of different cylinder heads.
Base T/As hit the showroom containing the 180hp version of the 400, which is better identified by the RPO code of L78. However, we're going to focus our attention on the W72 code. Our feature car, owned by Anthem, Arizona, resident Tim Blattner, was built with the optional 220hp W72, which sports a compression ratio of 8.1:1 with 320-lbs.ft. of torque using a Rochester M4MC four-barrel carburetor.
The exception to this optional engine would come compliments of the state of California, along with high altitude areas, where Oldsmobile's 403 was substituted for the Pontiac 400. Basic specs for the 403 engine include a 4.35 x 3.38-inch bore and stroke, 8.0:1 compression ratio, five mains, hydraulic lifters and a four-barrel carburetor. Horsepower came in at 185 and torque was 320-lbs.ft., measured at the flywheel.
Thanks to Pontiac's prolonged use of the 400 and the proliferation of the Olds 403, either engine can be easily rebuilt. Cams, cranks and pistons--and even upgrades--are quite plentiful. Bolt-on items are relatively inexpensive, such as a fuel pump at $33; a water pump costs $51.
TRANSMISSIONS
Unlike the days of old when you could select from an assortment of transmissions, the 1978 T/A was built with only two variants. The Turbo Hydra-Matic 350 automatic, as seen in Blattner's T/A, was standard equipment, coded as M33. This very common three-speed trans was mated with all three available engines.
Granted, automatics don't exactly conjure up visions of tire-shredding smoke shows. Fear not, as Pontiac did offer a Borg-Warner four-speed that had replaced the Muncie in 1975. However, there was a catch for both purveyor and purchaser: The four-speed was available only with the 220hp version of the 400. And since the 220hp 400 was not available in California, neither was the four-speed option.
As is often the case with these sturdy transmissions, they should last a lifetime of cruising, blended with a little thrashing from time to time. On the other hand, if you think the previous owner was practicing to be a stunt double for The Rockford Files or one of the Bandit movies, you might want to have the unit looked over for excessive wear and potential failures. Specialists can complete a rebuild with relative ease, but you can try your hand at a four-speed rebuild yourself with the purchase of a kit for $199.
DIFFERENTIAL
The semi-floating Hypoid axles were housed in a GM "corporate" 8.5-inch, 10-bolt unit that was shared with Pontiac's cousin, the Camaro. Depending upon the engine, transmission, and other options such as air conditioning, one of five final drive ratios was installed; 2.41:1, 2.56:1, 3.08:1, 3.23:1 or 3.42:1.
If the W72 400 engine was selected, it mandated a 3.23:1 gear with the automatic trans and a 3.42:1 with the four-speed. As such, Blattner's automatic T/A has a 3.23:1 ratio. Incidentally, he also has Pontiac's Safe-T-Track limited-slip differential.
Durability is not much of a concern with the 8.5-inch 10-bolt--it was intended as a heavy-duty axle for passenger cars and light trucks, and remains in service today in some half-ton GM trucks. Rebuild parts and gearsets in several ratios are readily available from multiple sources.
CHASSIS
As had been the case for several years, the T/A's wheelbase measures out to 108.1 inches, and the chassis was built via unit-body construction. A bolt-in subframe up front mounts the front suspension and engine/trans combo.
Right off the bat, we can tell you that rust can be an issue at the aft end, more so if the Safe-T-Track was installed. Thankfully, rear unit-body frame rails are available from several sources, including Ames Performance Engineering for $179 each. However, installing them is not an easy task; separating the factory spot welds, positioning the new rails and re-welding them is probably best left to an experienced body or restoration shop.
Connecting the Trans Am with the road is an independent front suspension and live rear axle. All the usual characters of a GM front suspension are in place: coil springs, upper and lower A-arms, tube shocks and an all-important anti-roll bar. Out back, the rear axle sits atop parallel leaf springs, as tube shocks and an anti-roll bar complete the assembly.
Yet, there is a difference between factory stock components from one T/A to another, and it comes down to one code: WS6. Essentially, the WS6 High Performance Package replaced the otherwise stock leaf springs with units rated 25-lbs.in. stiffer. The front anti-roll bar was increased to 1.25 inches in diameter, while polyurethane bushings were installed instead of standard rubber. The same was true for the rear anti-roll bar bushings, and the diameter was increased to 0.75 inches.
Tighter-valved shock absorbers were installed at the factory, and the normal 16.0:1 steering gear box was upgraded to a quick-ratio 14.0:1 unit. Bigger wheels were also part of the package, which we'll cover in a moment. Combined, these changes meant that the T/A could haul through the skidpad at 0.83g.
The suspension--for the most part--can be rebuilt. Items such as new tie rod adjusting sleeves are relatively cheap at just $13. A new center link costs $119, while a pair of rear leaf springs costs $219.
The one catch could be a Pitman arm, which according to one source is discontinued, but that doesn't mean that the NOS supply has been exhausted. But that shouldn't be an issue, since the Pitman arm on this chassis is really a "non-wear" item anyway, meaning that the pivot stud and socket are part of the center link--the Pitman is one piece of machined metal.
BRAKES
As had been the case since the start of the second generation F-body for 1970, all Firebirds feature front disc brakes as standard equipment, though T/As were power assisted. The front Delco-Moraine vented rotors are made of cast iron and measure 11 inches in diameter. At the opposite end, rear drums from the same source are also of cast iron, measuring 9.5 inches, and are finned to assist in cooling. Not surprisingly, rebuilding the system is simple, and finding parts is a matter of hitting the local parts store.
The stock system handles the 3,800-pound coupe just fine, and was in use straight up through the 1981 model year. However, starting in 1979, a rear disc package was available, code J65, as part of the WS6 package, which was standard on 10th anniversary models. If you can find this arrangement on a parts car, transplanting the system is a possibility--just make sure to take the master cylinder, power booster, proportioning valve and parking brake cables, too. Modern aftermarket rear disc systems are also available.
WHEELS & TIRES
Forget stamped steel and 14-inch tires. With the arrival of the Special Edition (SE), which is often referred to as the Bandit edition, came the aluminum "snowflake" wheels, which carried over to the 1978 models as standard equipment. Measuring 15 x 7 inches, they were offered in natural silver or were color-matched to the body.
Blattner's T/A, on the other hand, features the aforementioned WS6 package, which included the larger 15 x 8-inch Snowflakes. These wider wheels were offered in only two colors, gold or gray, and the tires of choice were Goodyear or Uniroyal 225/70R15s. Today, Blattner's car wears BFGoodrich 225/70R15 white letters at all four corners, since original reproductions are not currently available.
Finding pristine wheels to finish off a restoration might be a bit of a challenge, but there are alternatives. Sending out your worn wheels to a specialist is one option, and can be costly. Restoring them yourself is the other alternative, and will require time, care and patience. The details of the process are too lengthy to list here, but we can advise that the proper paint for the recesses--both gold and gray--is available from OEM Paints, and distributed through restoration suppliers like Classic Industries. See our Tech Restoration article in HMM#44, May 2007.
BODY & INTERIOR
Since the 1977 facelift was such a smash in the showroom, Pontiac opted to change little for 1978. As a result, both model years look essentially the same to the untrained eye, though there are indicators other than the VIN.
The T/A still featured front and rear spoilers, as well as fender spoilers. The hood decal remained a $66 option, but sport mirrors now came standard. Even the front fenders remained unchanged, still sporting air extractors above the decal behind the front wheels. One of the few noticeable changes was to the grilles, which were altered from a hexagonal pattern to a squared diamond pattern.
As one could expect, the Endura front bumper offers little to prevent minor parking lot dings. The same also applies to the wheel opening spoilers. Lower body panels also take a considerable amount of abuse from prolonged moisture exposure.
Again, popularity has its pluses for restorers: front grilles, $139; rocker panels, $85; quarter panels, $109; door skin, $92. Front fenders are also available from one supplier, though they have to be altered for the air extractors on an as-ordered basis. Patch panels exist for all vertical surfaces except the doors.
Inside, bucket seats, a leather-wrapped steering wheel and an engine-turned dash greet the driver. The buckets, usually dressed in vinyl, could have been ordered with cloth. Set into the dash is a rally instrument gauge package that includes a tach and clock as standard equipment.
Convenience options were plenty, including cruise control, and power locks and windows. Blattner's T/A features an unusual dealer-installed GM power sunroof and body side moldings. The sunroof is of the same type that was installed in same-year Cadillacs.
Interior items are available. Vinyl bucket seat kits cost $239 for a pair (a full $100 less than equivalent cloth kits), floor carpet costs $109, and you can replace rusted floor boards (a common problem area, especially if T-tops are present) by the section or half; the left half costs $95. Trunk floors, another area that can suffer with time, can be replaced for $169.
RESTORATION PARTS
Initially, one might suspect that restoration parts from the late Seventies would be slim pickings, at best. Not so. The tremendous popularity of GM's F-bodies has left fans with plenty of sources for body parts, mechanical bits and graphic packages alike. Some service items, such as tune-up parts, brake system parts and suspension bits, can still be purchased right at the counter of your local auto parts store.
PERFORMANCE PARTS
Back in 1978, the T/A was trying to maintain its image in the face of smog regulations and other obstacles, but there are those who think that the famed Firebird deserves more. Performance aluminum intake manifolds and cylinder heads are now available for the Pontiac and the Oldsmobile engines from Edelbrock, among some others, and plenty of camshaft options are produced by the major performance cam vendors like Comp Cams and Crane.
These cars also respond well to exhaust system upgrades, since the stock single catalytic converter doesn't flow as well as modern units, particularly if true duals are employed. Flowmaster and Magnaflow both offer large-diameter kits for the second-gen F-car, but they are designed for headers. Smog compliance can be an issue.
We briefly discussed brake upgrades; there are several options. Check with Stainless Steel Brakes Company for stock replacement or high-performance upgrades. The suspension can also be altered to handle the extra horses under the hood; Hotchkis Sport Suspension and Global West both make kits for this chassis.
OWNER'S VIEW
My first new car was the Cameo White 1978 Trans Am W72/WS6 that I still own, and I love the performance and the way they drive. I found this one for sale in Colorado in 2002, and I purchased it since it was a close match to what I already owned, plus it had the dealer/GM factory-installed power sunroof.
I knew it needed a lot of work: It had been in at least one accident, there were several attempts at rust repair, the seat covers had been redone with incorrect material, and the transmission was about to fall off the engine due to loose and missing bolts.
By the spring of 2006, I had completely restored the car back to its original numbers-matching condition. I take it out at least once a month, and it drives, handles and looks as expected.--Tim Blattner
WHAT TO PAY